Clone is a word that is now commonly used in many contexts in the United States. For example, rather than purchasing a name-brand computer, we might purchase its clone, which provides close to the same benefits but at a lower cost. If we’re running out of time, we might say that we wish we had a clone that could help us accomplish all our tasks. When biologists use the word clone, they are talking specifically about DNA molecules, cells, or whole plants or animals that have the same genetic makeup.
“Cloning” is achieved commonly in the world of horticulture by, for example, providing a branch or stem of a plant with water and the right environmental conditions and producing a new plant that is a clone, or genetically identical copy, of the original plant. In human reproduction, cloning occurs naturally when identical twins are produced.
Life scientists conducting research today often clone cells to obtain replicas of the bacterial, animal, or plant cells necessary to perform repeated experiments. They can also develop from a single cell large numbers of identical cells (a “clonal cell line”) that can be used for experiments and to test new medicines. Scientists clone DNA (“molecular cloning”) so that they have large quantities of identical copies of DNA for scientific experiments.
Cloning of adult animals, known as reproductive cloning, has become relatively widespread since the report of the birth of Dolly the sheep in 1997; Dolly was the first clone of a mammal produced from an adult cell. Mammals of five species—sheep, mice, pigs, goats, and cattle—have
now been successfully cloned from adult or fetal cells, and attempts are being made (so far without success) to clone monkeys, dogs, horses, and other animals in the same way. The cloning of mammals involves a process called nuclear transplantation or somatic cell nuclear transfer (SCNT). In biological terminology, clones are not replicas of each other, but contain identical genetic material.
The nuclear transplantation procedure is also used for a purpose distinctly different from cloning whole mammals. Like reproductive cloning, the process of nuclear transplantation to produce stem cells (also called “therapeutic cloning, nonreproductive cloning, or research cloning”) involves placing the DNA from one mammal into an enucleated egg (an egg from which the chromosomes have been removed). Thereafter, the egg is stimulated to divide. At the blastocyst stage of embryonic development (in humans, a 5-7 day old preimplantation embryo of about 150 cells), its inner cell mass is harvested and grown in culture for subsequent derivation of embryonic stem cells. These cells are then used for scientific and clinical investigations. Neither the cells nor the blastocyst are ever implanted in a uterus, as is required for reproductive cloning and the birth of an animal. Figures 1 and 2 in the Executive Summary illustrate the differences between the techniques of reproductive cloning and nuclear transplantation to produce stem cells.
This report, by a joint panel of the National Academies Committee on Science, Engineering, and Public Policy (COSEPUP) and the National Academies Board on Life Sciences (BLS), focuses on issues raised by the possible application of nuclear transplantation technology to the reproductive cloning of humans.
NATIONAL BIOETHICS ADVISORY COMMISSION
In 1997, after a report announced the cloning experiments that produced Dolly the sheep , President Clinton asked that the National Bioethics Advisory Commission (NBAC), chaired by Harold Shapiro, look at the issue of human cloning. The NBAC’s report, Cloning Human Beings , came to various conclusions, including the following (emphasis added):
“The Commission concludes that at this time it is morally unacceptable for anyone in the public or private sector, whether in a research or clinical setting, to attempt to create a child using somatic cell nuclear transfer cloning. The Commission reached a consensus on this point because current scientific information indicates that this technique is not safe to use in humans at this point. Indeed, the Commission believes it would violate important ethical obligations were clinicians or researchers to attempt to create a child using these particular technologies, which are
likely to involve unacceptable risks to the fetus and/or potential child. Moreover, in addition to safety concerns, many other serious ethical concerns have been identified, which require much more widespread and careful public deliberation before this technology may be used.”
The commission recommended, in part, the following:
“A continuation of the current moratorium on the use of federal funding in support of any attempt to create a child by somatic cell nuclear transfer.”
“An immediate request to all firms, clinicians, investigators, and professional societies in the private and non-federally funded sectors to comply voluntarily with the intent of the federal moratorium. Professional and scientific societies should make clear that any attempt to create a child by somatic cell nuclear transfer and implantation into a woman’s body would at this time be an irresponsible, unethical, and unprofessional act.”
“[Enactment of] federal legislation … to prohibit anyone from attempting, whether in a research or clinical setting, to create a child through somatic cell nuclear transfer cloning. It is critical, however, that such legislation include a sunset clause to ensure that Congress will review the issue after a specified time period (three to five years) in order to decide whether the prohibition continues to be needed. If state legislation is enacted, it should also contain such a sunset provision. Any such legislation or associated regulation also ought to require that at some point prior to the expiration of the sunset period, an appropriate oversight body will evaluate and report on the current status of somatic cell nuclear transfer technology and on the ethical and social issues that its potential use to create human beings would raise in light of public understandings at that time.”
“[Writing of] any regulatory or legislative actions undertaken to effect the foregoing prohibition on creating a child by somatic cell nuclear transfer … so as not to interfere with other important areas of scientific research. In particular, no new regulations are required regarding the cloning of human DNA sequences and cell lines, since neither activity raises the scientific and ethical issues that arise from the attempt to create children through somatic cell nuclear transfer, and these fields of research have already provided important scientific and biomedical advances. Likewise, research on cloning animals by somatic cell nuclear transfer does not raise the issues implicated in attempting to use this technique for human cloning, and its continuation should only be subject to existing regulations regarding the humane use of animals and review by institution-based animal protection committees.”
Other countries are also considering the issues and determining their policies. Different countries are coming to different conclusions about nuclear transplantation to produce stem cells, but they agree with the NBAC advice on reproductive cloning of humans.
CHARGE TO PANEL
The COSEPUP–BLS panel focused on the issue of human reproductive cloning. The National Academies provided the initiative and financial sponsorship for this study.
The time is ripe for a re-examination of cloning-related issues, inasmuch as it has been almost 5 years since the NBAC issued its recommendations. Much has happened scientifically since then. In addition, several organizations have indicated that they plan to clone humans. This report does not address the ethical issues that were the focus of much of the NBAC report. Instead, it provides an analysis focused on the scientific and medical aspects of human cloning.
In this report, the panel responds to the following questions in our task statement:
What does cloning of animals including humans mean? What are its purposes? How does it differ from stem cell research?
What is the state of science on cloning of animals? How does this science apply to cloning of people?
To what extent can our knowledge of assisted reproductive technologies inform the debate on human cloning?
What scientific and medical criteria should be used to evaluate the safety of cloning a person?
What issues of responsible conduct of research are raised by the prospect of cloning a person?
What process should be used to evaluate future scientific and medical evidence regarding cloning a person?
Based on the current scientific and medical evidence, should there be a moratorium on the cloning of a person? What are the implications of doing so? Of not doing so? If a moratorium is enacted, when should the issue be re-evaluated?
In this report, we will be discussing the concepts of bans and moratoriums. The panel uses the following definitions for each (from the unabridged version of Webster’s Third New International Dictionary).
Ban: “To prohibit by legal means or social pressure the performance, activities, dissemination, or use [of something]; … censure or condemna-
tion, especially through public opinion, social pressure, or moral or ethical considerations; severe disapproval [of something].”
Moratorium: “A suspension of activity; a temporary ban on the use or production of something.”
In developing its responses to those questions, the panel (see Appendix A) gathered and studied a large bibliography of scientific, veterinary, and medical literature (see Appendix B) and held 12 weekly conference calls for discussion. The panel also held a workshop on August 7, 2001, to hear testimony from and question some of the world’s foremost experts in embryology, animal cloning, assisted reproductive technologies, and associated public-policy issues (see Appendix C for the workshop agenda). Scientists who are now conducting research concerned with stem cells and those who plan to undertake reproductive cloning to create children also participated in the workshop. A transcript and sound files of the presentations at the meeting are available at the panel’s Web site (www.nationalacademies.org/humancloning).
ORGANIZATION OF THIS REPORT
Chapter 2 provides a basic introduction to cloning and its relation to stem cell research. Chapter 3 is an overview of the state of the science of animal cloning and a summary of its possible application to humans. Chapter 4 reviews the panel’s understanding of relevant assisted reproductive technologies. Chapter 5 describes the plans of those who wish to clone humans and provides the current policy and regulatory context. Chapter 6 contains the panel’s findings and recommendations.
1. WILMUT I, SCHNIEKE AE, MCWHIR J, KIND AJ, CAMPBELL KH. Viable offspring derived from fetal and adult mammalian cells. Nature 1997 Feb 27, 385(6619): 810-3.
2. NATIONAL BIOETHICS ADVISORY COMMISSION. Cloning Human Beings, Volume I: Report and Recommendations of the National Bioethics Advisory Commission. Rockville, MD. 1997 Jun. Online at: http://bioethics.gov/pubs/cloning1/cloning.pdf.